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vafc question/boost question

Old 12-11-2003, 12:37 PM
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Default vafc question/boost question

Hi i own a 98 gsr and just got some turbo stuff for it and have a question for yall, I plan on using 450cc dsm injectors and a vafc. I was wondering if it is possible to run more than 11 psi of boost without getting the cel, while using a vafc Cause i will be getting pistons and rods soon after my turbo setup is going and wonting to boost to say 15psi or so but i have heard that u get cel?? I was wondering if there is some special way to get rid of this or if you can get a chip made that will disable the cel from coming when you boost. thank you lots
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Old 12-11-2003, 01:30 PM
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Default Re:vafc question/boost question

No.

Your stock Honda MAP sensor will fail before you hit 15psi. IT's only good for about ~10 (some say 12, definately not 15). You probably could swpa to a 2 or 3 bar MAP sensor, then scale your MAP signal with the V-AFC, but, I wouldn't.

Once you start pushing over 10psi, it's time to invest in some real fuel management. Check into getting a conversion harness, to swap you down to OBD1 (if you're not already, I don't really now newer car ECUs) and use Uberdata to properly manage your boost.
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Old 12-11-2003, 01:50 PM
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Default Re:vafc question/boost question

yes jason, going from obd2 --> obd1 is a simple conversion harness and ecu away.
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Old 12-11-2003, 03:58 PM
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Default Re:vafc question/boost question

Originally Posted by ghettoturbo
not to knock your knowledge, but i ran 13 psi for months with no prob, and people have taken it higher on stock maps. Im sure its not smart or optimal, but it can be done.

..uh, and to fill in the gaps in your "knowledge", physically, yes, the MAP sensor will take much more boost. The problem is, however, due to the voltage scale of the MAP sensor, your readings stop at about ~10.5 psi, which is 5.0 volts.

Going higher than that is ridiculously dangerous as your fuel/timing maps will read from the last value available (which would be the last column at whatever RPM you are at).

..get what I'm saying?
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Old 12-12-2003, 04:08 AM
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Default Re:vafc question/boost question

Originally Posted by TurboEF9
Originally Posted by ghettoturbo
not to knock your knowledge, but i ran 13 psi for months with no prob, and people have taken it higher on stock maps. Im sure its not smart or optimal, but it can be done.

..uh, and to fill in the gaps in your "knowledge", physically, yes, the MAP sensor will take much more boost. The problem is, however, due to the voltage scale of the MAP sensor, your readings stop at about ~10.5 psi, which is 5.0 volts.

Going higher than that is ridiculously dangerous as your fuel/timing maps will read from the last value available (which would be the last column at whatever RPM you are at).

..get what I'm saying?
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Old 12-12-2003, 06:44 AM
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Default Re:vafc question/boost question

I think he was just saying it was possible. He did say it probably wasn't smart.

I think I misinterpreted the above statement with something along the lines of the AFC being able to run higher psi because the voltage tops off. Bobohc3d knows what I'm talking about.

I have ran 14 psi with no problems and Boosteded9 ran around 20psi with no cels.
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Old 12-12-2003, 09:58 AM
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Default Re:vafc question/boost question

Scaling with a V-AFC for extreme boost amounts also dangerous.

Looking at your fuel and timing maps for a visual, lets imagine that we did scale it. Each increment of pressure at the top of the grids would change to "squeeze in" higher pressures in the same table space.

What do we notice as this happends? Resolution is lost, and timing becomes radcially advanced in excess of 30 degrees in these high boost amounts!!

But lets get back to resolution. I don't know how many of you understand resolution, and how it effects tuning.

Say you have a regular 15x17 map. Stock MAP sensor pressures accross the top. Notice how each one skips a few readings as the columns read left to right.
What does this mean? That the same cell values are used for MAP readings between those column values.

Now if we think about our scaled MAP sensor signal that squeezes high boost amounts into the same area, the resolution becomes so shitty that you're using LOW fuel and HIGH timing values where they shouldn't be. The only way to correct this is modify your fuela nd timing maps (which is also difficult because you don't exactly know the scale) or decrease static timing reducing overall power.

What about a BTM to decrease timing per PSI.. yes, well, 1 degree per PSI ends up only being 10 degrees at 10psi.. this doesn't help us when our timing MAP has now been scaled and overall increase has advanced us more than that. So we're back to static timing, and loss of potential power.

Bottom line.. If you're going over 10psi, get real management.
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Old 12-12-2003, 05:08 PM
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Default Re:vafc question/boost question

ok i understand all that yall are saying. i am highly considering uberdata. does nebody else have ne word on uberdata/ uberteg from what i c it looks really good. i have already droppd my idea of buying a vafc because i can tune more accuratley and save alot of money with uberdata/uberteg. ty for all of yalls responsises they just saved me lots of money and probably my engine... later
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Old 12-12-2003, 06:11 PM
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Default Re:vafc question/boost question

Blake's software owns the OBD1 DIY tuning market. However, your limitation with the MAP sensor and "high boost" still exists as noted above.
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